The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, the approaches described in this section may not be prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In semiconductor integrated circuit manufacturing, it is conventional to test integrated circuits (“IC's”) during manufacturing and prior to shipment to ensure proper operation. Wafer testing is a well-known testing technique commonly used in production testing of wafer-mounted semiconductor IC's, wherein a temporary electrical connection is established between automatic test equipment (ATE) and each IC formed on the wafer to demonstrate proper performance of the IC's. Components that may be used in wafer testing include an ATE test board, which is a multilayer printed circuit board that is connected to the ATE, and that transfers the test signals between the ATE and a probe card assembly. The probe test card assembly (or probe card) includes a printed circuit board that generally contains several hundred probe needles (or “probes”) positioned to establish electrical contact with a series of connection terminals (or “die contacts”) on the IC wafer. Conventional probe card assemblies include a printed circuit board, a substrate or probe head having a plurality of flexible test probes attached thereto, and an interposer that electrically connects the probes to the printed circuit board. The interposer conventionally includes telescopic “pogo pins” or solder bumps that provide electrical connections between conductive pads on the printed circuit board and the interposer and between the interposer and conductive pads on the substrate. The test probes are conventionally mounted to electrically conductive, typically metallic, bonding pads on the substrate using solder attach, wire bonding or wedge bonding techniques
The pogo pin or solder bump connections used with conventional probe card assemblies have some significant limitations. For example, pogo pins use spring components that exert a high aggregate amount of force against the substrate when used in large numbers. The spring components used in pogo pins can also stick or wear out over time, resulting in a “floating contact.” Pogo pins are also generally very labor intensive to install, especially in high density applications, and do not have high planarity. They have high deflection capability but their coplanarity is poor. The high force exerted by pogo pins can deflect, misalign or even crack a substrate. Thus, pogo pins are not a scalable solution for higher density applications. Solder bumps do not have the same spring component-related problems as pogo pins, but solder bumps sometimes do not provide reliable electrical contact, resulting in floating contacts, i.e., an open circuit. Also, solder bumps are not readily repairable, since they are normally created using solder flow techniques that cannot be used to repair an individual solder bump. Solder reflow technology works well only for smaller reflow areas—scalability to 10 and 12 inches would be a problem.
Based on the foregoing, there is a need for a probe card assembly that does not suffer from limitations of conventional probe card assemblies.